Mammalian joints typically contain a small amount of synovial fluid which lubricates and moistens the joint surfaces to protect the joint against trauma, injury and degeneration. Some specific synovial fluid functions are to lubricate the joint surfaces, to absorb shocks to the joints, to bind acid and, possibly, to nourish some of the structural components of the joints. The synovial fluid is produced in the body by specialized cells, and the impairment of the fluid, i.e. decreased viscosity of the fluid due to the presence of degenerate cartilage products therein, is the principal source of the pain associated with degenerative joint diseases.
As a result, various modes of intra-articular treatment of arthritis have been proposed. Commercially available compositions including corticosteroids such as triamcinoline, prednisolone and hydrocortisone acetate are now in use in arthritis treatment. However, these compositions are difficult to use due to difficulties in dosage determination. Also, a number of adverse reactions have been observed in intra-articular steroid therapy. Consequently, corticosteroid treatments have fallen into relative disuse.
The use of hyaluronic acid has also been proposed for arthritis treatment. Hyaluronic acid appears to lubricate only the soft tissues of the joint which are not subject to heavy loading. Again, adverse side effects stemming from the treatment have been reported in some patients. Moreover, patients with clinical histories of local adverse reactions to the acid treatment appear susceptible to severe permanent joint damage.
Thus, there is interest in improved intra-articular treatments involving the injection of pseudo-synovial fluid into afflicted joints to replace or augment natural synovial fluid.